Gurgling in pipe at start and end of heating cycle

[61Raymond]

Hi, I am Christiane a customer who didn't know anything about central heating until 2 months ago.I got a replacement boiler Vaillaint Eco Plus 418, new 3 port valve, new pump system flushed with inhibitor and vented
I then started to have a whooshing noise and but crackle and pop which travelled through the whole system.However, radiators bleed, all boiling hot , but then all started again.
Cut a long story short, the system is now sealed with an expansion tank, a valve that allows surplus pressure to get out (also been replaced ) constant pressure is 1 to 1.5, so no leaks.However, still air
Boiler temperature now set to 60 degree ( rather than 72 as previously ) .Pump also in the right way ,arrow pointing towards the distributer valve.Runs lovely and quiet once on.
However , when the timer starts and the pump runs, there is an oh mighty gulp..gluck gluck to be heard in the pipe in the airing cupboard and in the radiator in the bedroom.Then it stops when the boiler starts so only lasts for about a minute or so.
At the end of the heating cycle, when the timer switches the boiler off, immediately the big gulp....gluck gluck appears followed by whooshing in the radiators until the over run finishes.

This is driving me and all plumbers absolutely bonkers.
Sealing the system has only made little difference...And again, all radiators are warm, no air trapped in any....sometimes changing the setting of one of the Thermostatic Valves in the bedrooms upstairs may trigger the gulp too......
I have now had 6 plumbers and all scratch their heads....meanwhile I am frightened to put the heating on which is pathetic..but it stresses me out so much.
Any help is much appreciated
.
P.S. notices yesterday that the pump switched itself off at 55 degree flow temperature and then back on when the temperature was reaching 57, did that twice whilst I was watching..is that right ?
Any ideas are welcome, I have photos too
Oh, it appears that the 3 port valve is not working properly as hot water appears to be on permanently, even when it s CH only.That will be replaced tomorrow hopefully.
Thank you so much

 

[TVP&H Ltd]

You've still got air in system. I wouldn't go pointing finger at faulty three port valve before checking wiring. Sounds like you need a more patient plumber......

 

[Unregistered]

My plumber has tried for 3 months, it s me who is impatient now !
Wiring in general or timer/ 3 port valve / boiler? Thank you

 

[Dotty]

It. Is. Air.

 

[61Raymond]

I know it is air, but it is not in the system when the boiler is running, it somehow is being created at the start and the end when timer starts /shuts down boiler and only pump is running .After 1 minute all is well and quiet , no air to be found anywhere all radiators hot , quiet as a mouse .....
Sorry, forgot to say ' thank you ' .Also, how does air get into a sealed system ? No leak to be found and the pressure isn't dropping either.......as

 

[stevetheplumber]

had something similar before on an s plan where the pump was starting before the valves were open causing pressure to build untill the valve let it go check the orientation of the three way valve make sure the hot is comming in on ab port
start system from cold and hold a hand on the three way

 

[61Raymond]

Thanks Steve will check.But what is the reason for it happening again when the timer switches boiler off Mind you, can hear valve moving and then it gurgles whilst pump overruns ...

 

[61Raymond]

Thanks Steve will check.But what is the reason for it happening again when the timer switches boiler off Mind you, can hear valve moving and then it gurgles whilst pump overruns ...Just checked hot comes from pump into ab , radiators a, tank b ....

 

[61Raymond]

Well, 3 port valve change and it now becomes apparent that if CH and HW is on all is well .The minute HW has reached temperature and switches itself off, a load of air and gurgle gets created instantly .
The minute the HW is on again and the diverted routes it through the tank all is well

Anybody with any ideas please ????